Review of the Functions of Archimedes' Spiral Metallic Nanostructures

21 Pages·2017·8.83 MB·English

nanomaterials
Review
Review of the Functions of Archimedes’ Spiral
Metallic Nanostructures
ZhongyiGuo* ID,ZixiangLi,JingranZhang,KaiGuo,FeiShen,QingfengZhouand
HongpingZhou*
SchoolofComputerandInformation,HefeiUniversityofTechnology,Hefei230009,China;
[email protected](Z.L.);[email protected](J.Z.);[email protected](K.G.);
[email protected](F.S.);[email protected](Q.Z.)
* Correspondence:[email protected](Z.G.);[email protected](H.Z.);
Tel.:[phone](Z.G.);[phone](H.Z.)
Received:28September2017;Accepted:18November2017;Published:22November2017
Abstract: Here,wehavereviewedsometypicalplasmonicstructuresbasedonArchimedes’spiral
(AS)architectures,whichcanproducepolarization-sensitivefocusingphenomenonandgenerate
plasmonicvortices(PVs)carryingcontrollableorbitalangularmomentum(OAM)becauseofthe
relationbetweentheincidentpolarizedstatesandthechiralitiesofthespiralstructures.Thesefeatures
can be used to analyze different circular polarization states, which has been one of the rapidly
developingresearchingtopicsinnanophotonicsinrecentyears. Manyinvestigationsdemonstrate
thatthemultifunctionalspiral-basedplasmonicstructuresareexcellentchoicesforchiralselection
andgeneratingthetransmittedfieldwithwell-definedOAM.Thecircularpolarizationextinction
ratio, as an evaluation criterion for the polarization selectivity of a designed structure, could be
effectivelyimprovedbyproperlymodulatingtheparametersofspiralstructures. Suchfunctional
spiralplasmonicnanostructuresarepromisingforapplicationsinanalyzingcircularpolarization
light,fullStokesvectorpolarimetricsensors,near-fieldimaging,andsoon.
Keywords: surface plasmon polaritons; circular polarization (CP); archimedes’ spiral structures;
orbitalangularmomentum(OAM)
1. Introduction
Polarization,asoneofthebasicpropertiesofthelight,iswidelyusedinmodernsensorsystems[1],
bywhichtheimportantinformationofreflectingobjectscanbeobtainedandrecognizedbecausethere
are different polarization characteristics for different objects. Additionally, this property can be also
employed in other applications, including optical communications [2], imaging polarimetry [3] and
microscopy[4]. Investigationsofacquiringthelinearpolarizationstatehavebeenperformedverywell
fromthevisible[5,6]toinfraredrange[7].Incontrast,itisstillachallengetodirectlydetectandanalyze
the circular polarization state, where a quarter wave plate and a linear polarizer are simultaneously
needed.However,theutilizationofbulkyopticaldeviceshinderstheminiaturizationofintegratedoptical
system[8,9].Theemergednano-scalemetallicstructures,whichproduceastronglypolarization-dependent
opticalresponse,canbeapromisingalternativeforobtainingpolarizationinformation.
Such Archimedes’ spiral plasmonic structures can be used as the circular polarization analyzer
forreplacingaquarterwaveplatecombinedwithalinearpolarizer,whichwillofferthepossibilityfor
potentiallyminiatureintegration.Atanearlytime,theArchimedes’spiralconfigurationsservedasspiral
antennasduetothebroadbandcharacteristicsascircularly-polarizedradiators[10–13],whichcanalso
provideanewideafortheunderlyingpolarization-dependenteffect.Inrecentyears,moreattentionhas
beenpaidtotheArchimedes’spiralstructurewithregardtoitsfunctionalityforcircularpolarization
analysisandgeneratingarbitraryorbitalangularmomentum(OAM)underilluminationsofcircular
Nanomaterials2017,7,405;doi:10.3390/nano7110405 www.mdpi.com/journal/nanomaterials
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0139 Ĺ 013\8'{L} ĸ \textkra LATINCAPITALLETTERLLWATITINHSAMCAULTLELETTERKRA
013\9capitaĹlacute{\L'}{L} LATINCAPITALLETTERLWITHACUTE
\capitalacute{L}
5
5
Nanomaterials 2017, 7, 405 3 of 22
j =m+l +s (1)
pv i i
where m is a parameter denoting the chirality of the PVL and si and li represent the SAM and OAM
oNf atnhome atienrciailds2e0n1t7 ,p7,h4o0t5ons. Owing to the geometric asymmetry, such a spiral structure can pro3voidf2e1
extra phase compensation. The phase compensation mechanisms of the spiral structure under
different incidences are illustrated in Figure 2. Figure 2a corresponds to the incident case of
compensation.Thephasecompensationmechanismsofthespiralstructureunderdifferentincidencesare
radially-polarized light, and Figure 2b,c corresponds to the CPL incidences with different chiralities
illustratedinFigure2.Figure2acorrespondstotheincidentcaseofradially-polarizedlight,andFigure2b,c
respectively for the proposed left-handed ASS. When the radially-polarized light or CPL
correspondstotheCPLincidenceswithdifferentchiralitiesrespectivelyfortheproposedleft-handed
illuminates the spiral plasmonic structure, the entire beam is in transverse magnetic (TM)
ASS. When the radially-polarized light or CPL illuminates the spiral plasmonic structure, the entire
polarization with respect to the slit wall, enabling SPPs excitation with initial phases from all
beamisintransversemagnetic(TM)polarizationwithrespecttotheslitwall,enablingSPPsexcitation
directions. The colored arrows indicate the propagating directions and the phase difference of the
withinitialphasesfromalldirections. Thecoloredarrowsindicatethepropagatingdirectionsandthe
generated SPP waves. As shown in Figure 2a, owing to the non-chirality of the radially-polarized
phasedifferenceofthegeneratedSPPwaves.AsshowninFigure2a,owingtothenon-chiralityofthe
light, the phase compensation is only provided by the geometric phase from the ASS whose chirality
radially-polarizedlight,thephasecompensationisonlyprovidedbythegeometricphasefromtheASS
iws −h1o.s Feocrh tihrael iCtyPiLs −in1c.idFeonrcteh, ethCePreL iisn cniod eOnAceM,t,h seore li i=s n0.o AOcAtuMal,lsyo, lth=e 0in.tAecrtaucatilolyn, tbheetiwnteeerna ctthioen inbectidweenetn
i
light and the anisotropic (inhomogeneous) nanostructure is the superposition of the SAM, the OAM
theincidentlightandtheanisotropic(inhomogeneous)nanostructureisthesuperpositionoftheSAM,the
and the ASS chirality on the SPPs’ interference. When the CPL carrying proper SAM illuminates the
OAMandtheASSchiralityontheSPPs’interference.WhentheCPLcarryingproperSAMilluminates
ASS, the ASS can act as a converter from the SAM to OAM [29,30]. When the rotation direction of
theASS,theASScanactasaconverterfromtheSAMtoOAM[29,30]. Whentherotationdirectionof
the spiral structure is the same as that of polarized incident light shown in the Figure 2b (namely,
thespiralstructureisthesameasthatofpolarizedincidentlightshownintheFigure2b(namely,the
the spiral structure and the incident light have the same chirality), the excited SPP wave carries the
spiralstructureandtheincidentlighthavethesamechirality),theexcitedSPPwavecarriesthephase
phase including the initial phase from the CPL and the geometric phase determined by the radius
includingtheinitialphasefromtheCPLandthegeometricphasedeterminedbytheradiusmismatch.
mismatch. In this case, the SPP waves reach the center of the ASS with opposite phases and
Inthiscase,theSPPwavesreachthecenteroftheASSwithoppositephasesandinterferedestructively,
iwntheircfherwe dilelsftorrumctitvheelyB,e wsshelicbhe awmillw foitrhma thtoep Boelossgeilc ablecahma rwgeitho faj top=ol2o.gWicahl iclehathrgeeR oCf Pjpvi n=c 2id. Wenhticlae steheis
pv
RCP incident case is given in Figure 2c, the SPP waves that arrive at the center of PVL have the same
giveninFigure2c,theSPPwavesthatarriveatthecenterofPVLhavethesamephaseandtheninterfere
phase and then interfere constructively, which will form the Bessel beam with a topological charge
constructively,whichwillformtheBesselbeamwithatopologicalchargeofj =0.Thus,thegenerated
pv
obfe ajpmv s=f o0r. inTchiduesn, ttlhigeh tgwenitehraotpedpo sbieteamchsi rafolirty ihnacvideednitf felirgenhtt towpiothlo goipcaplocshiaterg cehsiarnadlitoyb vhiaovuesl yddififfefererenntt
topological charges and obviously different field distributions.
fielddistributions.

Figure 2. Schematic diagram of the phase of the generated surface plasmon polariton (SPP) wave at
Figure2. Schematicdiagramofthephaseofthegeneratedsurfaceplasmonpolariton(SPP)wave
the virtual contour with the dashed black line inside the left-handed ASS by: (a) radial polarized
atthevirtualcontourwiththedashedblacklineinsidetheleft-handedASSby:(a)radialpolarized
lilgighht;t ;(b(b)) lelefft tcciirrccuullaarr ppoollaarriizzaattiioonn ((LLCCPP)) iinncciiddeennccee;; tthhee ttooppoollooggiiccaall cchhaarrggee ooff tthhee SSPPPP vvoorrtteexx iiss jjppvv == 22; ;
((cc)) rriigghhtt cciirrccuullaarr ppoollaarriizzaattiioonn ((RRCCPP)) iinncciiddeennccee;; tthhee ttooppoollooggiiccaall cchhaarrggee ooff tthhee SSPPPP vvoorrtteexx iiss jjppvv == 00. .
Reproduced with permission from [28]. Copyright Springer, 2015.
Reproducedwithpermissionfrom[28].CopyrightSpringer,2015.
The above-mentioned relationship can be denoted by the angular momentum conservation law
Theabove-mentionedrelationshipcanbedenotedbytheangularmomentumconservationlawand
and the dominant vertical electric field of the SPP wave at the concentric position of the PVL, which
thedominantverticalelectricfieldoftheSPPwaveattheconcentricpositionofthePVL,whichcanbe
can be simply expressed by the Bessel function as:
simplyexpressedbytheBesselfunctionas:
EzE(zr(,rϕ,ϕ,,zz))∝∝EE00eexxpp((iikkzzzz))eexxpp(i((is(is+i +mm)ϕ)ϕ)J)(sJi+(smi+)m()k(ρkrρ)r) (2()2 )
wwhheerree kkρρa annddk zkzd deneontoeteth tehwe awvaevneunmubmebrerra draiadlitaol tthoe thceen cteerntaexri saaxnisd apnedr ppeenrdpiecnudlaircutolatrh teom thetea lmpeltaatle ,
prleastpee, cretisvpeelyc,ti(vre,lϕy), is(rth,ϕe)p oilsa rthceo oprodlainr actoeocrodrirneastpeo cnodrirnegsptoontdhienCg atrot etshiea nCacortoersdiainna ctoe(oxr,dy)in. ate(x,y).
Ingeneral,thetransmittedintensitiesoftheASScanbesimulatedbyfinite-differenttime-domain
(FDTInD :gFeDnTeDralS,o ltuhteio ntrsa)nosrmthitetefidn itienetelenmsietinets moeft htohde (FAESMS :CcaOnM bSeO LsiMmuulltaiptehdy sbicys )wfinitihtet-hdeifpferroepnetr
tbimoue-nddoamryaicno n(FdDitiToDns: F[2D8T].DI nSoelxuptieornims)e onrt st,hteh feindiitfef eerleenmtetnrat nmsmetihttoedd (iFnEteMn:s iCtiOesM’ dSiOstLri bMuutilotinpshcyasnicsb)e
detectedbyametallicaperturednear-fieldscanningopticalmicroscope(NSOM)fiberprobesystem[31].
Nanomaterials 2017, 7, 405 4 of 22
with the proper boundary conditions [28]. In experiments, the different transmitted intensities’
distributions can be detected by a metallic apertured near-field scanning optical microscope (NSOM)
fiber probe system [31].
Nanomaterials2017,7,405 4of21
3. Different Structural Constructions
3. DifferentStructuralConstructions
3.1. Pure Archimedes’ Spiral Plasmonic Lens
3.1. PureArchimedes’SpiralPlasmonicLens
The single-turn Archimedes’ spiral plasmonic lens was designed and investigated as a
Thesingle-turnArchimedes’spiralplasmoniclenswasdesignedandinvestigatedasaminiature
miniature circular polarization analyzer in 2009 by Q. Zhan [31,32]. The schematic diagram of a
circular polarization analyzer in 2009 by Q. Zhan [31,32]. The schematic diagram of a single-turn
single-turn left-handed Archimedes’ spiral plasmonic lens under CPL illumination is illustrated in
left-handed Archimedes’ spiral plasmonic lens under CPL illumination is illustrated in Figure 3,
Figure 3, in which the width of spiral slit is set as 200 nm. The spiral constant of r0 in the above
in which the width of spiral slit is set as 200 nm. The spiral constant of r in the above algebraic
algebraic formula was set as r0 = 2Λ, and the incident wavelength was chosen0 to be 808 nm.
formulawassetasr =2Λ,andtheincidentwavelengthwaschosentobe808nm.
0

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wwiitthh CCPPLL iilllluummiinnaattiioonn.. AA ssiinnggllee--ttuurrnn lleefftt hhaannddeedd ssppiirraall ((LLHHSS)) sslliitt wwaass eettcchheedd tthhrroouugghh tthhee ggoolldd ffiillmm,,
wwhhiicchh wwaass ddeeppoossiitteedd oonn tthhee ggllaassss ssuubbssttrraattee.. RReepprroodduucceedd wwiitthh ppeerrmmiissssiioonn [[3311]].. CCooppyyrriigghhtt AAmmeerriiccaann
CChheemmiiccaall SSoocciieettyy,, 22001100..
SSuucchh aa ssppiirraall ppllaassmmoonniicc lleennss hhaass bbeeeenn iinnvveessttiiggaatteedd aannaallyyttiiccaallllyy aanndd eexxppeerriimmeennttaallllyy ffoorr iittss
sseennssiittiivviittyy ttoo tthhee iinncciiddeennttC CPPLLp poolalrairziaztaitoinons.sW. Withithin icnrceraesainsignrga draiudsiuosf othf ethspe isrpalirsalilt ,sltiht,e tshtreu scttruurcetucaren
cgaenn egreanteeraatpeh aa spehsahseif tshtoiftt hteo pthroe ppargoaptainggatSinPgP SwPaPv we,awveh,i cwhhwicihll wfinilal lfliynaaldlyju asdtjtuhset pthhea spehoafseth oef StPhPe
SwPaPv ewaatvteh aet stthreu csttruurcatlucreanl tceern.tHere. nHcee,nscue,c hsuachm ai nmiaitnuiaretugreeo gmeoemtryetsrtyr ustcrtuucrteuprer opcreoscseessseths ethfee afteuarteuroef
ofof cfuosciunsgintgh ethCeP CLPwLi twhitahg aiv geinvehna nhdaenddneedsnseisnst oinatoc oan cfionnefdinsepdo stpwoth iwlehdileef odceufoscinugsitnhge tChPe LCwPLit hwtihthe
tohteh eorthhearn dheadnndeesdsninestos aindtoo nau dt-oshnaupt-esdhappoeindt ,pwoihnict,h wcahnicbhe cuasne dbefo ursseedle cfotirn gsetlheectpinogla trhizea tpioonlasritzaatetsioonf
sCtaPtLesi nocfi dCePnLc eisn.cBideesnidceess,. fBoerstihdiess,t yfpore tohfissp tiyrpale polfa ssmpioranli cplleansms,othneicr eleisnsn,o thneereed itso naod jnuesetdth teo caednjtursatl
tahlieg ncmenetnratl( aaxliiaglnlymseynmt m(aextriaicllsyt rsuycmtumreest[r3ic3 –s3t6r]urcetquureirse d[3t3o–a3l6i]g nretqhueicreendt etroo faltihgenc itrhceu lacrelnyt-epro loafr izthede
cbiercaumlaarlnyd-ptohlearcizeendte rbeoafmth eanpdla stmheo nciecntleern so),f wthhei chplawsimllobnrioca dleenns)t,h we hreicahl awppillli cbartoioandsenin tphea rarellaell
aimppalgicinagtio[3n7s] i.n parallel imaging [37].
TThhee nneeaarr--ffiieelldd iinntteennssiittyy ddiissttrriibbuuttiioonnss aarree sshhoowwnn iinn FFiigguurree 44aa,,bb ffoorr lleefftt--hhaannddeedd AASSSS uunnddeerr CCPPLL
iilllluummiinnaattiioonnss,,w whhicihcha raerme emaesuasreudrebdy baym ae tmalleictaalpliecr atupreerdtunreeadr- fnieeladr-sfciaenldn isncgaonpntiincagl ompitcircoaslc ompiecr(NosScOopMe)
(fNibSeOrpMro) bfei.bTehr epmroebaseu. rTedher esmueltassaugrreede wreeslulwltsi thagthreeet hweoerlelt iwcailtahn athlyes isthaesosrheotiwcanl inanFaiglyusries 4acs,d ,sehxocwepnt fionr
Faigduarrek c4ecn,dte, reixncteepnts iftyord ais tdriabrukt iocennutenrd einrtRenCsPitiyll udmisitnriabtiuotnioans suhnodwern RinCFPig iullruem4ainbaetcioanu saest hsehmowetna lliinc
Faipgeurrtue re4da NbSecOaMusefi btehrep mroebtealilsicm aopreersteunrseidti vNeStoOtMra nfsivbeerrs aplrcoobme pios nmenotsre[ 3s8e,3n9s]i.tivHeo wtoe vterra,nssuvcehrsaanl
ceoxmpeproimneennttsa l[3p8h,e3n9o].m Heonwonevdeore, ssuncoht caonn terxapdeicrtimaecnotnafli npehdensopmoteinnotnh edooreesti cnaolta cnoanlytrsaisdsicint cae ctohnefpineeadk
sdpeotet citned tshiegonraeltoicfatlh eanNaSlyOsMis fsiibnecrep rthobee pineatkh edfeotceucsterdeg sioignnuanl doefr tRhCeP NinScOidMen fciebiesrs tpilrlotbweo -itnim these hfiogchuesr
rtehgainotnh uatnudnedr eRrCLPC Pinlciigdhetnincec iidse sntcilel. two-times higher than that under LCP light incidence.
SSuucchh aa ssyymmmmeettrryy bbrrookkeenns strturucctuturereo fofth tehesp siprairlasll istlliet nlesncsa ncabne beae seilaysiflayb rfaicbartiecdatiendto ingtoold gfoilldm failnmd
asnelde csteivleeclytivfoecluys fLocCuPs iLncCidPe inncceidaenndcRe CaPndin RciCdPen icneciindteonscpea itniatolly s-pseaptiaarlalyte-dsefpiealrdast.eBdy fimeledasn. sBoyf mNSeOanMs oofr
NtwSoO-pMh ootorn tfwluoo-rpeshcoetnocne mfliucororsecsocpenyc[e4 0]m,tihcerossucrofapcye i[n4t0en],s itthyed issturribfaucteio ninstceannsbiteyd edtiescttreibdu.Ttihoengs ecnaenra tbede
dSePtPesctperdo.p aTghaet inggentoewraaterdd thSePPcesn tperroopfatghaetipnlgas mtoownaicrdle ntshein tceernfetreer coonf stthruec tpivlaeslymwonitihc thleenssa mineteprhfearsee
coorndsetsrturcutcivtievleyly wwiitthh tthhee ospapmosei tepphhasaes e,owr hdicehstlreudcttiovaelzye rwotihth-o rtdheer eovpapnoessicteen tpfhiealsde,d iwstrhiibcuht iolendw tioth aa
zceernotrtahl-opredaekro revaadnoensucet-nsth afpieeldd sdecisotnrdib-uortdioenr ewvaitnhe sac encetnfiterladl dpisetarkib uotri oan ,dreosnpuetc-tsivhealpy.ed second-order
evaneBsoctehntth feieeldxp deirsitmriebnuttaiolann, dreasnpaelcytitviceallyr.e sultsofsurfaceintensitydistributionsunderRCPandLCP
incidencesmatchwellwiththesimulations[32]. ByadjustingthestructureparametersofPVLand

incidentwavelength,theopticalfieldcanbefocusedintothefar-fieldregion,whichisdemonstratedby
finite-differencetime-domainsimulationandexperiments[41]. Inthiswork,ther ofthesingle-turn
0
Nanomaterials2017,7,405 5of21
ASSissettobe2µm,andthefreespacewavelengthischosentobe405nm. Atightlyfocusedspot
withthesizeof330nmnearlyat3.5µmfromthemetalsurfacecanbeobtained,whenthestructural
chiralityisoppositethechiralityoftheCPLincidence. Thisfocusingenhancementinthefar-field
regionisbecauseoftheshortwavelength[42,43]andtheconstructiveinterferenceoftheSPPwave
atthecenteroftheplasmoniclens. Thesefar-fieldpropertiesmakeitpossibletoprobethesignalof
sampleinthefar-field,thereforetakingtheplaceofconventionalnear-fieldopticaldevices. which
Nsuanffoemratferroiamls 2a01v7e, 7r,y 40s5h o rtworkingdistance. 5 of 22

FFiigguurree 4.4.M eMaseuarseudrende arn-feiaerld-fisecladn nsicnagnonpintigc alomptiiccraols compiecr(oNsScoOpMe )i(mNaSgOeMsa) ttihmeaagire/sg oaldt itnhteer faacier/(gao,bld);
iRnetperrofadcuec (ead,bw);i tRhepperromdiusscieodn fwroitmh [p3e1r]m,Ciosspiyornig fhrotAmm [3e1ri]c, aCnoCphyermigihcat lASomceiertiyc,a2n0 1C0h.eAmniaclaylt iScaolccieatlcyu, l2a0ti1o0n.
Asunrafalyceticinatle ncaslictyuldaitsitornib usutirofnac(ec ,din);teRnespirtoyd duicsetdribwuittihonp e(rcm,dis);s iRonepfrroomdu[c3e2d], wCoitphy rpigerhmtOispsitoicna lfSroomcie t[y32o]f,
ACompeyrriciga,h2t 0O09p.tFicoarl aSnocLiHetSy loefn sAsmtreurcitcuar,e 2u0n09d.e Fro(ar ,ca)nR LCHPSi llleunms isntartuiocntuarne dun(bd,der) L(aC,cP) iRllCumP iinllautmioinn.ation
and (b,d) LCP illumination.
3.2. Multiple-TurnSpiralSlit
Both the experimental and analytical results of surface intensity distributions under RCP and
Afterthesingleturnspiralslitwasinvestigated,theperformanceofmultiple-turnASSshownin
LCP incidences match well with the simulations [32]. By adjusting the structure parameters of PVL
Figure5wasreportedin2011[44]. Basedonthesamephasematchingtheory,suchamultiple-turn
and incident wavelength, the optical field can be focused into the far-field region, which is
spiral structure works in a more effective and practical way for the application of plasmonic lens
demonstrated by finite-difference time-domain simulation and experiments [41]. In this work, the r0
becausetheincreasingturnswillimprovethecouplingeffectsofthegeneratedSPPwave.
of the single-turn ASS is set to be 2 μm, and the free space wavelength is chosen to be 405 nm. A
Theschematicdiagramoftheleft-handedfive-turnspiralslitetchedthrough300-nmsilverfilm
tightly focused spot with the size of 330 nm nearly at 3.5 μm from the metal surface can be obtained,
asaplasmoniclensisshowninFigure5a. TheRCPilluminatesalongthenegativez-coordinateon
when the structural chirality is opposite the chirality of the CPL incidence. This focusing
thestructurewiththewavelengthof660nmasdepictedinFigure5b. Figure5cillustratesthephase
enhancement in the far-field region is because of the short wavelength [42,43] and the constructive
retardationsofthegeneratedSPPwavealongthepropagationdirectionwithcolorfularrows,which
interference of the SPP wave at the center of the plasmonic lens. These far-field properties make it
meansthattheexcitedSPPwavecarryingtheinitialphaseattheASSexperiencesphaseretardations
possible to probe the signal of sample in the far-field, therefore taking the place of conventional
proportionaltothedistancefromtheslittothecenterwhenitpropagatesfromtheslittothecenterof
near-field optical devices. which suffer from a very short working distance.
theASS,asweanalyzeabove. Additionally,theywillkeepthesamephaseoncetheyreachthecenter
oftheASSandfinallyleadtoaconstructiveinterferencepattern.
3.2. Multiple-Turn Spiral Slit
The FDTD simulation results for such multiple-turn ASS demonstrate its advantages for
After the single turn spiral slit was investigated, the performance of multiple-turn ASS shown
generatingahighquality,zero-orderevanescentBesselbeamandrelativehighfocusingdepthofthe
in Figure 5 was reported in 2011 [44]. Based on the same phase matching theory, such a
focusspotunderRCPillumination. WhileundertheLCPincidence,adarkcenterwillbeobtained,
multiple-turn spiral structure works in a more effective and practical way for the application of
asexpected. Thus,suchmultiple-turnASSwillbequiteusefulindetectingthepolarizationcharacters
plasmonic lens because the increasing turns will improve the coupling effects of the generated SPP
oftheincidentCPL.Nevertheless,afactshouldbenotedthattheintensitywillreachthemaximum
wave.
whentheturnsareincreasedtobefiveowingtothelimitationofthepropagatinglengthoftheSPP
The schematic diagram of the left-handed five-turn spiral slit etched through 300-nm silver
wave. Suchamultiple-turnASScanfindpotentialapplicationsforfocusingbeams,intensityactuating,
film as a plasmonic lens is shown in Figure 5a. The RCP illuminates along the negative z-coordinate
CPLpolarizationanalysis,andsoon.
on the structure with the wavelength of 660 nm as depicted in Figure 5b. Figure 5c illustrates the
phase retardations of the generated SPP wave along the propagation direction with colorful arrows,
which means that the excited SPP wave carrying the initial phase at the ASS experiences phase
retardations proportional to the distance from the slit to the center when it propagates from the slit
to the center of the ASS, as we analyze above. Additionally, they will keep the same phase once
they reach the center of the ASS and finally lead to a constructive interference pattern.
USV Symbol Macro(s) Description
USV Symbol Macro(s) USV Symbol MDaecsrcor(ips)tion Description
Nanomaterials2017,7,405 0392 Β \textBeta GREEKCA6PIoTAfL2L1ETTERBETA
039N2anomatΒerials 201\7t, e7x, t4B0e5t a 0393 Γ \te0x3t9G2amma Β \GtReExEKtCBAePtITaALLETTERBETA GREEKC6A PoITfA 2L2L ETTERGAMMAGREEKCAPITALLETTERBETA
0393 Γ \textGamma 0394 Δ \te0x3t9D3elta Γ \GtReExEKtCGAaPmITmAaLLETTERGAMMA GREEKCAPITALLETTERDELTA GREEKCAPITALLETTERGAMMA
0394 Δ \textDelta 0395 Ε \te0x3t9E4psilonΔ \GtReExEKtCDAePlITtAaLLETTERDELTA GREEKCAPITALLETTEREPSILONGREEKCAPITALLETTERDELTA
0395 Ε \textEpsilon 0396 Ζ \te0x3t9Z5eta Ε \GtReExEKtCEApPsITiAlLoLEnTTEREPSILON GREEKCAPITALLETTERZETA GREEKCAPITALLETTEREPSILON
0396 Ζ \textZeta 0397 Η \te0x3t9E6ta Ζ \GtReExEKtCZAePtITaALLETTERZETA GREEKCAPITALLETTERETA GREEKCAPITALLETTERZETA
0397 Η \textEta 0398 Θ \te0x3t9T7heta Η \GtReExEKtCEAtPaITALLETTERETA GREEKCAPITALLETTERTHETA GREEKCAPITALLETTERETA
0398 Θ \textTheta 0399 Ι \te0x3t9I8ota Θ \GtReExEKtCTAhPeITtAaLLETTERTHETA GREEKCAPITALLETTERIOTA GREEKCAPITALLETTERTHETA
0399 Ι \textIota 039A Κ \te0x3t9K9appa Ι \GtReExEKtCIAoPtITaALLETTERIOTA GREEKCAPITALLETTERKAPPA GREEKCAPITALLETTERIOTA
039A Κ \textKappa 039B Λ \te0x3t9LAambda Κ \GtReExEKtCKAaPpITpAaLLETTERKAPPA GREEKCAPITALLETTERLAMDAGREEKCAPITALLETTERKAPPA
039B Λ \textLambda 039C Μ \te0x3t9MBu Λ \GtReExEKtCLAaPmITbAdLaLETTERLAMDA GREEKCAPITALLETTERMU GREEKCAPITALLETTERLAMDA
039C Μ \textMu 039D Ν \te0x3t9NCu Μ \GtReExEKtCMAuPITALLETTERMU GREEKCAPITALLETTERNU GREEKCAPITALLETTERMU
039D Ν \textNu 039E Ξ \te0x3t9XDi Ν \GtReExEKtCNAuPITALLETTERNU GREEKCAPITALLETTERXI GREEKCAPITALLETTERNU
039E Ξ \textXi 039F Ο \te0x3t9OEmicronΞ \GtReExEKtCXAiPITALLETTERXI GREEKCAPITALLETTEROMICRONGREEKCAPITALLETTERXI
039F Ο \textOmicron 03A0 Π \te0x3t9PFi Ο \GtReExEKtCOAmPiITcArLoLEnTTEROMICRON GREEKCAPITALLETTERPI GREEKCAPITALLETTEROMICRON
03A0 Π \textPi 03A1 Ρ \te0x3tAR0ho Π \GtReExEKtCPAiPITALLETTERPI GREEKCAPITALLETTERRHO GREEKCAPITALLETTERPI
03A1 FFiigΡguurree 55.. \(ta(ea)x )tSSRcchhhoeemmaatitci0 cd3dAia3iaggraramm Σoof fleleftf-th-\hatane0nxd3tdAeS1edid gmmmauultlΡitpiplele-t-utur\nrGtn RepExEplKtalCRasAhsmPomIToAoLnLniEciT cTlEeRlenRnHsO;s ;(b(b) )RRCCPP lilgighhtG tRaEaEtKt aCaA PITALLETTERSIGMA GREEKCAPITALLETTERRHO
03A3 wwaΣavveelleenngg\tthht eooxftf S66i66g00mn anmmil l0iu3llmAu4minianteasteaΤsl oanlognthg\ ettenh0xee3tgA Tn3aateuigvaetziv-Σceo ozr-cdoino\arGdttReeiEnxE(Kcta)CStAeisP cgIT(hmAcaeL)mL EsTacTthEiRecSmIdGMiaaAtgicr admiaogfrtahme roeGflR aEttEhiKveCeA PITALLETTERTAU GREEKCAPITALLETTERSIGMA
03A4 rpehlΤaatsiveeo fps\hutaersfxeat cToeafup slausrmfaoc0en3 Awp5laavsemsoenΥx cwiteadvebs\y teet0xhx3cetAiU4tspepsdiir labolyns Τltihteu nsdpei\rrGtaRRelE xECsKtlPCTiAtaiP ulIuTlAunLmdLEeiTnTrE aRRtTiACoUnP. TillhuemdiinffaetrieonntG. RcTEoEhKloeCrA PITALLETTERUPSILONGREEKCAPITALLETTERTAU
03A5 dairfΥrfoerwenstr ec\potrleoexsrte Uanprtsrotihlweosnd rief0fp3erAree6snetnpth tahΦsee sd’iifnfecr\reetnme0tx3 etpAnP5hthaiosfetsh’ eiΥneclreecmtriec\nGtfitRe EeoxElKtfd CUtAEphPszIeTi.A leLRolLeeEnTcpTtrErRoicUdP uSfIiLceOelNdd wEzi.t hRepperromdGiusREscEieKodCnA PITALLETTERPHI GREEKCAPITALLETTERUPSILON
03A6 wfriΦothm p[e4r4m]\.itCsesoxioptnPyh rfiirgohmt S[4p04r3i]n.A C7georp,y20ri1Χg1h.t Spri\ntge0ex3rtA,C 62h0i11. Φ \GtReExEKtCPAhPiITALLETTERPHI GREEKCAPITALLETTERCHI GREEKCAPITALLETTERPHI
03A7 Χ \textChi 03A8 Ψ \te0x3tAP7si Χ \GtReExEKtCCAhPiITALLETTERCHI GREEKCAPITALLETTERPSI GREEKCAPITALLETTERCHI
03A83.3. HThyΨebr iFdDSTp\iDtrea xlstPiPmlsaiusmlaotnioic0n3L Aer9nessultsΩ for su\tceh0x3 tAmO8muegltaipΨle-turn \GtAReExSEKtSCP AsPdiITeALmLEoTTnERsPtSrIate its advanGtRaEgEKeCsA PITfAoLrL ETTEROMEGAGREEKCAPITALLETTERPSI
03A9 Ω \textOmega 03AA Ϊ \te0x3tAI9otadieΩresis \GtReExEKtCOAmPeITgAaLLETTEROMEGA GREEKCAPITALLETTERIOTAWITGHRDEIEAKLYCATIPKITAALLETTEROMEGA
03AgAenerTathΪieng Aa Sh\Stiegxhtm Iqoeutnaatdliiiotenyr,ee sdziesroa-boorvdeer ceavnan\"eo{s0\nc3teAleyAnxtt IBcooetsuas}Ϊpelle betah\mGetRe ExaEKtrnCIadAodPt ITiraAaedLlliLlaEeyTtrT-ieEpvRseoIiO slThaArWigiITzhHeD dIfAoLYcTucIKoAsimngp odneepntth ooff GREEKCAPITALLETTERIOTAWITHDIALYTIKA
tchierc ufolcaurlsy -sppoo\lta" r{ui\znteeddxetrIin oRtcaiCd}Pe03n AiclBeluimntionΫaStPioPnw. \Wa"v{he\itsle.ex OtuUnpnsdtihelero nb}thaes e\L"oC{f\Ptth exientsIcioindtage}lnec-etu, ran dAaSrSk, acehnytebGrRr EiEwdKCisAlplPI TiAbrLaeLl ETTERUPSILONWITHDIALYTIKA
03AoBpbltaasimneΫodn,i calse n\e"s{x\hptaeescxttbeUedpes. nilTof0hun3}urAtCsh, ersupcrάho pmosueld\ti'pf{0o\l3ertA-eBetxuntrahnlap nhAΫac}iSnSg twh\eiG"lRl{cE \EoKtbuCeeAxp PtIlTUqiAnpLusLgiEitTleTeoE fRnfiUu}PcsSiIeLeOfnNucWlyI THi[Dn4IA 5LY,d4TIeK6At]e(GcaRtEsiEnKsgShM AoLtwLhLeEnT TERALPHAWITGHRTEOEKNOCSAPITALLETTERUPSILONWITHDIALYTIKA
03ApColarizάation c\h'a{r\atecxtetarsl pohaf }0th3AeD incideέnt CPL\'. {0N\3tAeeCvxteerpthsielάloens}s, a \fG'aR{Ec\EtKt SesMxhAtoLaLulLEplTdhTaE R}bAeLP HnAoWtITeHdTO NthOSat theG RiEnEtKeSMnAsLiLtLyET TEREPSILONWGITRHEETKONSMOSALLLETTERALPHAWITHTONOS
in Figure 6). It combines a single-turn ASS with a single-turn arranged triangular aperture array,
03AwDill reaέch the\ 'm{\atexxitmepusmil o0wn3}AhEen theή turns \a'{r0\e3t AeiDnxtcerteaa}sέed to \bG'eR{E \EfKtiSevMxeAtL eLopLwEsTiTilEnRogEnP} SItLoON WthITHeT OlNiOmS itatiGoRnEE KoSMf ALtLhLeET TERETAWITHTGORNEOEKSSMALLLETTEREPSILONWITHTONOS
03ApEcroouppalgiήnagtinbgo tlh\e'nt{hg\ettherx atodeft itaah}lea 0nS3dPAFPth weaavzieίm. Suuthcha\l 'a{p0 \3omtAleEauxrtlitiziopattlaei}ήo-tnucrno mA\Gp'SR{EoS\EnKt cSeeMaxnAtnLteL stLfEaioTn}fTEdCR EpPTAoLWt.IeTTHnThtOiNeaOlSe xappeprliimcaGeRtEinEoKtnaSMslA aLfLnoLErdT TERIOTAWITHGTROENEOKSSMALLLETTERETAWITHTONOS
03AFnumerίicalres\u'{l\tstevxetriioftya}th03eBe0xpectaΰtionso\"f{0t\3htAeeFxdtuepssigilnίonvaecruyte\wG}'R{Ee\ElKtlSe.MxAAtLiLsoLEtsTahT}EoRwIOTAnWiITnHTFONigOSure6a,GtRhEEeKSsMpALiLrLaETlTERUPSILONWGITRHEEDKIASLMYATLIKLALEATNTDERTOIONTOASWITHTONOS
03Bf0aorcruasningΰegm beeanmt\o"sf{, \3int2etxeistnouspsisctiyel laoe0ncs3atBtuc1ruaitatein}nggu,α lCarPLap pe\ortltea0ux3rrtBieaz0slaptehitoacnh eΰadnainlytosi\saG",R{ E1a\E5nKt0SedMx-A ntsLuLmopL EsoTgiTnlEoR.o lUndPaScIfiLuOlNtmeW}ITcHaDInALYcToIKuAApNlDGeRTEObENKoOSStMhALtLhLEeTTERALPHA GREEKSMALLLETTERUPSILONWITHDIALYTIKAANDTONOS
03B1radialαandth\eteaxztiamlpuhtahalp03oBl2arizatiβoncom\tpe0ox3tnBb1eenttasofαCPL[\4Gt7ReE]xE.KtWSaMlAphLhLeaLnETTtEhRAeLPaHAzimuthalcomGpREoEKnSMeAnLLtLiEsTTERBETA GREEKSMALLLETTERALPHA
03B32i.n3c. iHdeynbβtritdo Sthpi\ertaterlx iPtabnlaegstumaloanriac0p L3eBer3ntus res’γarray,c\otne0xs3ttBrg2urgcatimvmeaβfocusin\GgtReEcxEaKtnSbMeAbtLaeLLaETcThERiBeEvTAedowingtothGeREiEnK-SpMAhLLaLsEeTTERGAMMA GREEKSMALLLETTERBETA
03B3surfaTcheγep laAsmS\Sot nexsmtagetrngtahtmieomnatwed0o3 Be4qaubaolvseiδ decsaann d\toae0nxd3ltBjyad3 ecletcnaotuappγleer tutrhe\e.Gt RWeExEKrthaSgeMdrAngiLaaLtmLlhElmTyeaT-ErpRaGodAlMiaaMrAlizcoedm pocnomenptoGisRnEiEenKnScMti AdLLeoLnEfTt T ERDELTA GREEKSMALLLETTERGAMMA
03Bc4tiorctuhlearδtlryi-apnoglu\atrleaizxretdadep lietnractiudree0n3acBre6r ainyt,od SeζPstPru wcta\ivvteee0x3stfB. oz4Oectunas itnhgeδ bwaislel b\oGtefRe ExEtaKthcSdehMe AilsLetLivanLEegTdTlEeR-oDtEwuLTrAinn gAtSoS,t hae hoyubtGr-RioEdEfK -sSpMpAhiLraLaLsEleT TERZETA GREEKSMALLLETTERDELTA
03B6 ζ \textzeta 03B7 η \te0x3tBe6ta ζ \GtReExEKtSzMeAtLaLLETTERZETA GREEKSMALLLETTERETA GREEKSMALLLETTERZETA
03Bp7sluarsfmacoeηnpicl alesnm\sto ehnxatsse atbtaetehne futw0r3toBh8eerq puraolθpsoidseeds a\fonter0dx 3etBant7dhhejaatnacceinnηtga tpheer tc\uGotReruEexEpKt.SelMiStnAauLgLc LheETfTfaEiRclEieTeAfnt-chya [n4d5e,4d6]s p(aisr aGsRlhEEtoKrwSiMaAnnL LgiLnlEeT TERTHETA GREEKSMALLLETTERETA
03BF8leignusrcea θn6).f oIctu \cstoetmhxtebtihRneCetasP aa ns0di3nBLg9lCeP-tuinrnιc idAeSnSc\ etwei0nxi3ttBthgo8 raido itsfafienrθgelne-ttpuar\ntGttR eeEaxErKrtnrStMsahAenoLtLgfaLeEtTdhTE eRtTreHilEaeTAnctgruiclafir ealdpedritsuGtrRrEeiEb KuaSMrtAirLoaLnyLEs,T .TERIOTA GREEKSMALLLETTERTHETA
03Bc9Tohueplmineιga sbuorteh\d ttheinxett gerranidsoiittaayl adn0is3dtB rAtihbeu taizoiκnmsubtyhaN\l tSpe0Oxo3tBlMka9arpifzpoaartitohιne cloefmt-\phGtRoaeExnEnKtedSgMnreAitdLsoL tLsoEapTfT iECrRaIPOlTLAt.r iTahneg leexlpeenrsimuGenRnEdEtKeaSrlM ARaLnLCLdEPT TERKAPPA GREEKSMALLLETTERIOTA
03BnAaunmdeLrCiκcPal irlleus\umtletixnst avktaeiporpinfays athr0ee3 BseBhxopwecntaλitnionFisg ou\ftr eet0hx37teBlaA ad,bmeb,sdriagensκp veecrtiyv \ewGtlRyeeEx.ElKlt.BSk MAaeApLsspLi aLdsEhTeTosER,wKtAhnPPe Ains pFiirgaulraer r6aan, gGtRheEemEK sSeMpnAiLtrLaLoElTf TERLAMDA GREEKSMALLLETTERKAPPA
03BaBtrrriaannggeuλmlaernatr o\ratf ey3x2t( lsiaysmombsdmcaeelet0sr3y tBrCbiarnokguenlμa)rd aopeesr\ttnue0oxr3tetBmsBnu eetecdhethλde incteon ta\rGt Ra1eEl5xEKt0aSl-lManiAgmLmbLndL mEagTToeERlndLtA MfoiDlfAmth ceanp lcaosumpolenG RibEcEoKltSehMnA LtsLhLteEoT TERMU GREEKSMALLLETTERLAMDA
03BrCtahdeiasli naμgnudl atrhiet\y taepzxotimminuuttohfaill lpuomlairniaztaitoinone ictohmer\,ptweo0x3nhtBemiCncughtrsce oeakfn μCoPvLer c[4o\G7tmRe]E.xEe KtWSmtMhuAheLeLdnLEi TfTtfiEhRceMu Ualtzyimofuuthsainl gcothmepsocnaennnti nisg GREEKSMALLLETTERMU
\textmugreek 03BD ν \textnu \textmugreek GREEKSMALLLETTERNU
03BiDmnceicdheanνnt istom tfho\etr eixtmrtinaaugnignugl.ar0 3aBpEertureξs’ arra\yt,e 0xc3tBoxDnistrucνtive fo\cGtuReEsxEiKtnSnMguA LLcLaEnTT ERbNeU achieved owinGRgEE KtSoM ALtLhLeET T ERXI GREEKSMALLLETTERNU
03BiEn-phTashξee dsuisrtf\aatncecexe txpbileatswmeoenn0s3t BhFaet spthireοa lttwrioa n\egtqeu0xu3ltaBaoErlm aiscpirdeorentξsu raenadr r\aGtaRyedExEjKataSxncMideALnLttLh ETeaTEpsRpXeIrirtaulres.l itWishseent atshGR0eE.E 7Kr5SMaAλdLsLipaLEplT ,TEROMICRONGREEKSMALLLETTERXI
03BcFroemsupltoinοnegnitn isa \itpnehcxitadosemeincdtr itofofne trh0e3enC ct0reiaonfg3uπl/a2r .aTph\etreet0uxr3tarBpedFi iaarlraaynο,d daezsitmr\uGutcRetEtxEhiKvtaSoeMlm AifpLocLorcLlEouaTnTsrEiiRnzOagMIt CiwRoONinll cboem apcohnieevnGeRtdEsE KooSfwMACiLnLPLgELT TERPI GREEKSMALLLETTEROMICRON
03Ct0hoa sthae πo/u2t-pohf\-atpsehexatdpsieif fesurernfac0ce3e.C 1pTlhaesrmeρfoonrse ,aat\n tet0ohx3vteCre0 hrtoawllo 2πeqpuhaal s\esGtiReddExEeiKtfsSpfM eiAarLenLnLdEcT TeEaRdmPIjaacyenbte aopbetaritnueredG.R EbESeKutSMwcAhLeL eLaEnT TERRHO GREEKSMALLLETTERPI
03Cl1SefPtP-hwanρadveeds esxp\ctireitaxelt drthraoiatnthgeles 0lp3eCinr2as lctarnia ςnfogcuulsa rt\hateep0 x3eRtCrgC1truPsri egamnaadrρr aLyCaPn \idGntRecEtxEhiKtdeSreMhsnAopLcLieLrE aTiTnlERtsoRlHi tOd,ilfefaedreinngt ptoatctoerGnnRsEsEtK rouSMfcA tLtLihvLeEeT TERFINALSIGMGAREEKSMALLLETTERRHO
03Ce2ilnetcetrrfiecς rfeienlcde da\\itttseettxxrhttiebgvraucsrteisinogimgtneamsar. 0wT3hCit3eh mtheeasσhuirgehde isn\\ttttfieee0xxne3ttlCsdvs2iaityrgesm ndiahgismataςnricbeumtieo\\nGntttRees.ExxE bKttTSgvyhMra AusrNLisLsSgiL,EmgOTtamThaEMReF IcNfoAoLrmS ItGbhMAien laetfito-hnaonfdGtRehEdEeK sSsMppAiLirLraLaElTl TERSIGMA GREEKSMALLLETTERFINALSIGMA
03Ct3srliiatnwglietσh lesnpsi rua\ntlledyxe-tars riRrgamCnaPg eadn0d3tCr 4LiaCnPg uilllτaurmapinear\tttiuoe0xrn3etCst3 aaarurrea yshsσohwown nin\iGt nRFeExiEFgKtiSsugMirAugeLmLr ae7LEaT6T,EbbR,S cIrGaeMnAspfoecctuivseRlyC. PBleiGsgRiEhdEKteSsiMn,A LttLohLeEaT TERTAU GREEKSMALLLETTERSIGMA
03Cs4mpiorrael atτirgrhantlgye\fmtoecexuntsttea oudf stprioatn0a3gCnu5dladr eafrorυcauys (tshy\emtLe0mx3CtCeuP4tprslyiig lbhorntoτiknetno)a d\dGotReoeExEnsKt uStnMatoA-uLstL hLnEaTepTeERedTdA Utdhies tcreibnutrtaiol nalwigGinRtEmhEKeaSMndAtL aLoLrEfkT TERUPSILON GREEKSMALLLETTERTAU
03Ct5cheen ptelra.υsTmhoensiuc\ ptleeexnrtisou ptrositi itlehoseno sf0int3hCg6euclaormitbyφi npaotiinotn\ otlefi0 ex3itlCilgn5urmpthhiienhaυtiigohne reipt\hoGtRweeExrEKet, SurwMpcAshLoiLinlLcEovhTnTe EcrRasUinPoS ILnoOvNeeffirccoiemnecy thaen GddREitEfhKfiSeMcAufiLlLetLlyEdT TERPHI GREEKSMALLLETTERUPSILON
03Co6efn uhsainncφge tmheen stc\catoenxmntigpnragprh emidewch0ita3hCn7itshme ffoorχrm imeralyg-i\dnteeg0sx3. itCgc 6nhiedpuφreASS\GtpReElxEaKtsSgMmrApLohLinLEiTcTElRePHnIs. ThefieldenhGaREnEKcSeMmALLeLnETtTERCHI GREEKSMALLLETTERPHI
03C7atthefχocusin\gteaxntdchtihepowerconversioneffi0c3iCe7ncyofχthecirc\GutRelEaxEKtrScMphAioLLlaLErTiTzERaCtHioI nanalyzerareincreased GREEKSMALLLETTERCHI
by39.53%and94.69%bynumericalstudies,respectively.
Intermsofthehybridplasmoniclens,azeroth-order(second-order)evan1e8scentBesselvortex
beam will be obtained under RCP (LCP) incide1n8t illumination with higher coupling efficien1c8y.
Forbothcircularly-polarizedilluminations,donut-shapedpatternswithadarkcenterareobtainedin
Nanomaterials2017,7,405 7of21
experimentalresultsowingtothelowcouplingefficiencyofthelongitudinalfield,whilethedetected
peaksignalinthefocusregionforRCPincidenceisobviouslyhigherthanthatwithLCPincidence.One
ofthemethodstoimprovethecouplingefficiencyofthelongitudinalfieldistousetheworn-outNSOM
fiberprobewitha200-nmaperture. Therefore,adetectorwithdiameterofdplacedinthefocusregion
candetectthesignalsfordistinguishingtheRCPandLCPwell. Additionally,thecircularly-polarized
extinctionratiobetterthan16canbeattainedwithadiameteroftheapertureas0.3λ,whichshowsthat
iNtacnaonmabteeriaalsh 2i0g1h7,- 7e,f 4fi0c5i e ncyminiaturecircularpolarizationanalyzer. Besides,anarrayofthesehy7b orf i2d2
Nplaansommaotenriiacls l2e0n1s7,e 7s, c40a5n bealsousedinparallelnear-fieldandpolarimetricimaging. 7 of 22

Figure 6. Scanning electron microscope(SEM) image of a plasmonic lens th at consists of a
Figure 6. Scanning electron microscope(SEM) image of a plasmonic lens that consists of a
Fspigiruarlely -6a.r rSacnagnendi ntgri aenlgecutlraorn s umbi-carpoesrctoupree (SaErrMay) eimtcahgeed oinf toa ap lgaoslmd ofnilimc l(ean) s anthda ta choynbsrisidts sopfi raal
spirally-arrangedtriangularsub-aperturearrayetchedintoagoldfilm(a)andahybridspiralplasmonic
spplairsamllyon-aircr laenngse cdo mtrbiainnignugl atrh es uabrr-aayp eorft utrriea nagruralayr eatpcehretudr eins two itah gsoinldg lef-itlmur n( aA) SaSn (db )a f ahbyribcraitde ds pwiritahl
lenscombiningthearrayoftriangularapertureswithsingle-turnASS(b)fabricatedwithfocusedion
pfolacsumseodn iioc nle bnesa cmo m(FbIiBn)i nmgi ltlhineg a. rRraeyp roofd turicaendg wuliathr appeerrmtuisrseiso nw fitrho msi n[4g6le].- tCuornp yAriSgSh (tb O) pfatibcrailc aStoecdie wtyi tohf
beam(FIB)milling.Reproducedwithpermissionfrom[46].CopyrightOpticalSocietyofAmerica,2012.
fAomcuesreidca i,o 2n0 b12e.a m (FIB) milling. Reproduced with permission from [46]. Copyright Optical Society of
America, 2012.

FFiigguurree 77.. MMeeaassuurreedd NNSSOOMM nneeaarr--fifieelldd iinntteennssiittyy ddiissttrriibbuuttiioonn iimmaaggeess ooff tthhee lleefftt--hhaannddeedd aarrrraannggeedd ssppiirraall
Fttrriiigaaunnrggeuu 7llaa. rrM aapepaeesrrutturureredea NarrrSarOayyMu un ndnedearerr(-a f()iaeR)l dCR PiCnaPten nadnsi(dtby )( bdL)iCs LtPrCiibnPuc tiindiocenind ciemen.acRgee.e psRr oeofpd truhocede udlecfwet-diht hawnpidteher mdp aiesrrsrmiaoninsgsfeirodonm s pfr[i4or6ma]l.
tC[r4io6ap]n.y gCruioglpahryt raOipgpehtrtit cuOarlpeSt ioacrcarilea Styyo ucoinfedAtyem ro e(fa rA)ic mRa,Ce2rP0ic 1aa2n,. d20 (1b2). LCP incidence. Reproduced with permission from
[46]. Copyright Optical Society of America, 2012.
3.4. ATShSe wdiitshtaanCcoen bceentwtreiceAn nthnue lsapriGrarol otvrieangular aperture array and the spiral slit is set as 0.75 λspp,
resulTTtihhneeg dcinois mtaa bnpichneaa sbtieeo tndwifeofefenrAe tnShcSee saopnfi dr3aπal /t2cr.io aTnnhcgeeun rltaarrdi ciaapal nearnntuudlr aear zaigrmrraouyot hvaaenl,d pa toshlaeshr siozpwairtniaol nisn lcitoF miisg pusoeretn ea8ns, t0sh. 7ao5sf λCalsPpspLo,
rheassu alt iπn/g2 ipnh aa speh daisfefe dreifnfceere. nTchee roeff o3rπe/,2 a. nT hove erraadlli a2lπ a pndha aszei mdiufftehraeln pceo lmaraiyza btieo onb ctoaminpedo nbeentwts eoefn C SPPLP
been proposed and investigated in theory for realizing the selection for CPL in the far-field [48].
hwaasv ae sπ /e2x cpihteadse adt iftfheer esnpcier.a Tl htreiraenfogruel,a ar na poveretruarlle 2aπr rpahya saen dd iftfheer esnpcier aml asyli tb, el eoabdtianinge tdo bceotwnseterunc StiPvPe
TheimprovedperformancecomparedwiththepureASScomesfromthefactthattheexistenceof
winatevrefse reexncciete adt atht et hcee nstperir awl itthri atnhge uhlaigrh aepste rftiuelrde eanrhraayn caenmde ntht.e Tshpuirsa, lt hseli tc, olmeabdiinnagt ioton coof ntshter uscptiirvael
thecircularannulargroovecanscattertheSPPsatthegrooveintothepropagatingwaveandthen
isnlitte rwfeitrhe nscpei raatl ltyh-ea rcreanntgeerd w tritihan tghuel ahri gahpeesrtt ufireel da rernayh asnhcoewmne nint. FTihguusre, t6hbe ccaonm fboicnuast iRoCn Po fl itghhet sinptiora al
converge the propagating waves into the far-field. The scattered light by the annular groove can
smliot rwe ittihg hsptliyr aflolycu-asrerda nsgpeodt atrniadn dgeufloacru asp tehretu LreC Par lriagyh ts hinotwo na idno Fniugtu-sreh a6pbe cda nd ifsotrciubsu tRioCnP wliigthht ai ndtaor ak
interfereconstructivelyordestructivelyinthefar-field,whichmakeitavailableandconvenientfor
mceonrtee rt.i gThhtely s ufopceursieodri tsipeso to af nthde d ceofmocbuisn athtieo nL CliPe liing htht ei nhtoig ha edro pnouwt-eshr acpoendv edrissitornib ueftfiiocnie nwciyth a an dd atrhke
practicalapplicationsinthefar-field,wherethesignalcanbedetectedbyconventionalopticaldevices.
cfieenldte re. nThhaen scuempeerniot rictoiems poafr ethde wcoimthb itnhaet ifoonr mliee rilny -tdhees ihgingehde rp puorwe eAr ScSo npvlearssmioonn eicf filceinens.c yT haen df itehlde
SimulatedresultsindicatethatsuchasimplifiedstructurecanbealsousedtofocustheincidentCPL
feinelhda necnehmaenncte mate ntth ec ofmocpuasriendg wanitdh tthhee pfoowrmere rlcyo-ndveesrigsinoend epffuicriee nAcyS So fp ltahsem ocinriccu llaern sp. oTlahreiz afiteioldn
intothefar-fieldregioneffectively,iftherotationdirectionofpolarizationlightisoppositethechirality
eannhaalynzceerm aerne ti nactr etahsee df obcyu 3si9n.5g3 %an adn dth 9e4 .6p9o%w ebry cnounmveerrisciaoln s teufdfiiceise,n rceys poefc ttihveel yc.i r cular polarization
oftheASS.Additionally,thefullwidthathalfmaximum(FWHM)ofthefocalspotcanalwaysmaintain
analyIzne rte arrme si nocfr ethaese hdy bbyr i3d9 p.5l3a%sm aonndi c9 4le.6n9s%, a b zye nroutmh-eorridcaelr s(tsuedcoiensd, r-oesrdpeerc)t ievvealyn.e s cent Bessel vortex
beamIn w tielrl mbes oobf ttahien ehdy burnidd eprl aRsCmPo n(LicC lPe)n isn, cai dzeenrot tihll-uomrdinera t(isoenc ownidth-o hrdigehr)e re vcaonuepslcinengt e Bffeiscsieenl cvyo.r Fteoxr
bbeoathm cwiriclul lbaer loyb-ptaoilnaeridz eudn dilelur mRCinPa t(iLonCsP, )d ionnciudte-snht aiplleudm pinaattteiornn sw witihth h aig hdearr kc ocuenptlienrg a ereff iocbietnaicnye. dF oinr
beoxpthe rciimrceunltaarll yr-epsoullatrsi zoewd iinllgu mtoi ntahteio nlosw, d oconuupt-lsihnagp eefdf icpiaetntecyrn so fw tihthe alo dnagriktu cdeinntaelr faiereld o, bwtahinileed t hine
edxepteecrtiemde npteaalk rseisgunlatsl ionw thineg f otcou st hree glioown fcoor uRpCliPn gin ecfidfiecniecnec yis oobf vtihoeu slloyn hgiigtuhdeirn tahl afni etlhda, t wwhitihle LtChPe
dinectiedcetendc ep. eOanke s iogfn tahle i nm tehthe ofdosc utso rimegpiornov feo rt hReC cPo uinpcliindgen ecfefi cisie onbcvyi oouf sthlye hloignhgeitru tdhianna lt hfiaetl dw iist hto L uCsPe
itnhcei dweonrcne-. oOunt eN oSfO thMe fmibeetrh opdros bteo wimitphr oav 2e0 t0h-ne mco uappelirntugr eef. fTichieenrecyfo oref , tah ed leotnecgtiotur dwinitahl dfiiealmd eist etro oufs de
tphlea cwedo rnin-o utht eN fSoOcuMs friebgeiro pnr ocbaen wdiethte cat 2t0h0e-n smig anpaelsr tuforre . dTihsetirnegfouriesh, ian dg ettehcet oRr CwPi tha nddia mLCetPe r wofe ldl.
pAldacdeidti oinna ltlyh,e t hfeo ccuirsc urleagriloyn-p ocalanr izdeedte ecxt titnhcet iosnig rnaatliso bfoertt edr itshtianng u16is hcainng b et haett aRinCePd wanitdh aL CdPia mweetlelr.
Aofd tdhieti oanpaelrltyu,r teh aes c 0ir.c3uλl,a wrlhyi-cpho lsahroizweds tehxatitn ict tcioann rbaet iao hbiegthte-re ftfhicaine n1c6y c mani nbiea tautrtaei ncierdcu wlairth p ao ldairaizmaetitoenr
of the aperture as 0.3λ, which shows that it can be a high-efficiency miniature circular polarization
Nanomaterials 2017, 7, 405 8 of 22
analyzer. Besides, an array of these hybrid plasmonic lenses can be also used in parallel near-field
and polarimetric imaging.
3.4. ASS with a Concentric Annular Groove
The combination of ASS and a concentric annular groove, as shown in Figure 8, has also been
proposed and investigated in theory for realizing the selection for CPL in the far-field [48]. The
improved performance compared with the pure ASS comes from the fact that the existence of the
circular annular groove can scatter the SPPs at the groove into the propagating wave and then
converge the propagating waves into the far-field. The scattered light by the annular groove can
interfere constructively or destructively in the far-field, which make it available and convenient for
practical applications in the far-field, where the signal can be detected by conventional optical
Ndaenvoimcaetser. iaSlsim20u17l,a7t,e4d0 5results indicate that such a simplified structure can be also used to focu8s otfh2e1
incident CPL into the far-field region effectively, if the rotation direction of polarization light is
opposite the chirality of the ASS. Additionally, the full width at half maximum (FWHM) of the focal
lessthanthehalfwavelengthofincidentlight,whichcanovercometheshortcomingofthenear-field
spot can always maintain less than the half wavelength of incident light, which can overcome the
characteristicsoftheintensitydistribution.
shortcoming of the near-field characteristics of the intensity distribution.

Figure 8. Schematic diagram of the designed structure under the illumination of the RCP plane wave
Figure8.SchematicdiagramofthedesignedstructureundertheilluminationoftheRCPplanewave
along the positive z-direction. Reproduced with permission from [48]. Copyright Springer, 2011.
alongthepositivez-direction.Reproducedwithpermissionfrom[48].CopyrightSpringer,2011.
The schematic diagram (Figure 8) shows a left-handed ASS milled into a 300-nm silver film
Theschematicdiagram(Figure8)showsaleft-handedASSmilledintoa300-nmsilverfilmwith
with a concentric annular groove as a plasmonic lens, and the corresponding parameters are also
aconcentricannulargrooveasaplasmoniclens,andthecorrespondingparametersarealsoindicated.
indicated. The circularly-polarized plane wave illuminates along the positive z-direction with
Thecircularly-polarizedplanewaveilluminatesalongthepositivez-directionwithwavelengthof660nm,
wavelength of 660 nm, and the ASS width w1 and the groove depth h are set as 100 and 50 nm,
andtheASSwidthw andthegroovedepthharesetas100and50nm,respectively.WhentheRCPlight
respectively. When t1he RCP light is incident on the plasmonic lens structure, SPP waves excited by
isincidentontheplasmoniclensstructure,SPPwavesexcitedbytheASSwillpropagatealongthemetal
the ASS will propagate along the metal surface, and then, they are scattered by the concentric
surface,andthen,theyarescatteredbytheconcentricannulargrooveintopropagatingwavesintofree
annular groove into propagating waves into free space. Eventually, the scattered propagating
space.Eventually,thescatteredpropagatingwavesfromtheannulargroovewillinterfereconstructively
waves from the annular groove will interfere constructively because of the same phase on the
becauseofthesamephaseonthez-axis.
z-axis.
Figure 9 shows the simulated |E|2 distribution in the x-z-plane for the left-handed spiral
Figure 9 shows the simulated |E|2 distribution in the x-z-plane for the left-handed spiral
plasmonic lens shown in Figure 8 with concentric annular groove radius r = 0.90 µm under RCP
plasmonic lens shown in Figure 8 with concentric annular groove radius r22 = 0.90 μm under RCP
and LCP incidence, respectively. Such a left-handed combined structure focuses RCP light into a
and LCP incidence, respectively. Such a left-handed combined structure focuses RCP light into a
centralspotefficiently,asshowninFigure9a. Owingtotheexistingscatteringphasefunctionofthe
central spot efficiently, as shown in Figure 9a. Owing to the existing scattering phase function of the
scatteredlightcausedbytheconcentricannulargroove,theintensityalongthepropagationdirection
scattered light caused by the concentric annular groove, the intensity along the propagation
isenhancedgradually(thereisanobviousdifferenceinintensitypointbypoint)intothefar-field.
direction is enhanced gradually (there is an obvious difference in intensity point by point) into the
TheFWHMofthefocusiscalculatedtobe0.44λ smallerthanthehalfwavelengthofincidentlight
far-field. The FWHM of the focus is calculated 0to be 0.44 λ0 smaller than the half wavelength of
(λ );whilesuchastructurefocusesLCPincidentlightintoaringwithadarkcenterspotasshownin
inc0ident light (λ0); while such a structure focuses LCP incident light into a ring with a dark center
Fspigout raes9 Nsbahn,oodmwuatneer itailons 2 tF0h1i7eg, 7ud, r4ee0s5 t 9r bu,c dtiuvee itnot tehrfee dreensctreuocftisvcea titnetreerdfelriegnhcteo offt hsecaStPtePrewda lvigehint othf ethfea rS-9fiP ofeP 2l 2dw .ave in
the far-field.

Figure F9i.guTreh 9e. Tsihme usilmatueladte|d E||E|22 ddiissttrribibuutitoinosn isn itnhe txh-ez-pxl-azn-ep floarn tehef olerft-thhaendle sfpt-irhaal npdlassmpoinraicl lpenlas smonic
lens unudnedrerR RCCPP iinnccididenecnec (ea) (aan)da LnCdP LinCciPdenincec i(dbe).n Rceepr(obd)u.cedR ewpitrho pdeurmceidssiowni tfrhomp e[4r8m]. iCssoipoynrigfhrot m [48].
CopyrigShptriSnpgerri,n 2g0e1r1,. 2011.
The focus effect of similar combined structures with five concentric annular grooves R = 0.58,
0.90, 1.22, 1.54 and 1.86 μm are also investigated. Simulated results reveal that the focus depth can
be modulated by adjusting the number and radius of concentric annular grooves. The
demonstrated potentials make this structure have great applications in the areas of optical detection,
imaging, and so on. This plasmonic lens provides new trains of thought for later studies on
combing a multiple-turn spiral slit with several grooves, which can improve the coupling efficiency
and elongate the focal depth effectively.
3.5. ASS Combined with Coaxial Archimedes’ Spiral Gratings
A combined plasmonic structure by ASS with coaxial Archimedes’ spiral gratings (ASG) on
both sides of the gold film (Figure 10) has also been proposed and investigated in theory by our
group, which is designed based on the same spin-dependent polarization-sensitive and
spin-dependent focusing effect of the ASS [28]. The designed structure is sensitive to incident
polarization of CPL, and it can realize the focusing and defocusing effects under the illumination of
different CPL effectively owing to the existence of ASG.

Figure 10. Schematic diagram of the proposed structure under the illumination of the circular
polarization plane wave along the positive z-direction (from glass side); (a) a single-turn left-hand
spiral slit surrounded by Archimedes’ spiral gold grating on both sides of the metal film; (b) lateral
view of the structure along the location of the line depicted in (a). The red arrows represent the
propagation of SPPs. The incident light is coupled into SPPs through the spiral slit, and the SPPs
generated from the corresponding slits at each side have the opposite direction of propagation. The
Nanomaterials 2017, 7, 405 9 of 22

Figure 9. The simulated |E|2 distributions in the x-z-plane for the left-hand spiral plasmonic lens
under RCP incidence (a) and LCP incidence (b). Reproduced with permission from [48]. Copyright
NanomSatperriianlsg2e0r1, 72,071,14.0 5 9of21
The focus effect of similar combined structures with five concentric annular grooves R = 0.58,
0.90,T 1h.e22f,o c1u.5s4e affnedct 1o.f86si mμmila rarceo malbsoin iendvsetsrtuigctautereds. wSiimthufliavteedco rnecseunlttrsi creavnenaul ltahragtr tohoev efoscRus= d0e.5p8t,h0 .c9a0n,
1b.2e2 ,1m.5o4daunldat1e.d86 µbmy aaredajulssotiinngv estthigea tendu.mSibmeru laatendd rersaudltisurse veoafl thcoatntcheenftoriccu sadnenputhlacra ngbreomovoedsu. laTtehde
bdyeamdojunssttirnagtetdh epnoutemntbiearlsa mndakraed tihuiss ostfrcuocntucerne thriacvaen gnruelaatr agprpoolivcaesti.oTnhse ind etmheo anrsetarast oedf oppottiecnatli dalestemcatikoen,
tihmisasgtirnugct,u arendha vsoe gorena. tTaphpisl icpaltaiosmnsoinnitch eleanrse apsroofvoipdteicsa lndeewte cttriaoinn,si moaf gtinhgo,uagnhdt sfooor nl.aTtehri ssptuladsmieso noicn
lceonmspbrionvgi da emsnueltwiptlrea-tiunsrno fspthiroaulg shlitt fworitlha tseervseturadli egsrooonvceosm, wbihnigcha cmanu litmippler-otuvren thspei rcaoluspliltinwgi tehffsiecvieenracyl
garnodo veelos,nwgahtiech thcea nfoicmapl rdoevpethth eeffceocutipvleinlyg. efficiencyandelongatethefocaldeptheffectively.
3.5. ASSCombinedwithCoaxialArchimedes’SpiralGratings
3.5. ASS Combined with Coaxial Archimedes’ Spiral Gratings
AcombinedplasmonicstructurebyASSwithcoaxialArchimedes’spiralgratings(ASG)onboth
A combined plasmonic structure by ASS with coaxial Archimedes’ spiral gratings (ASG) on
sidesofthegoldfilm(Figure10)hasalsobeenproposedandinvestigatedintheorybyourgroup,
both sides of the gold film (Figure 10) has also been proposed and investigated in theory by our
which is designed based on the same spin-dependent polarization-sensitive and spin-dependent
group, which is designed based on the same spin-dependent polarization-sensitive and
focusingeffectoftheASS[28]. ThedesignedstructureissensitivetoincidentpolarizationofCPL,
spin-dependent focusing effect of the ASS [28]. The designed structure is sensitive to incident
anditcanrealizethefocusinganddefocusingeffectsundertheilluminationofdifferentCPLeffectively
polarization of CPL, and it can realize the focusing and defocusing effects under the illumination of
owingtotheexistenceofASG.
different CPL effectively owing to the existence of ASG.

Figure 10. Schematic diagram of the proposed structure under the illumination of the circular
Figure 10. Schematic diagram of the proposed structure under the illumination of the circular
polarization plane wave along the positive z-direction (from glass side); (a) a single-turn left-hand
polarizationplanewavealongthepositivez-direction(fromglassside);(a)asingle-turnleft-handspiral
spiral slit surrounded by Archimedes’ spiral gold grating on both sides of the metal film; (b) lateral
slitsurroundedbyArchimedes’spiralgoldgratingonbothsidesofthemetalfilm;(b)lateralviewof
view of the structure along the location of the line depicted in (a). The red arrows represent the
thestructurealongthelocationofthelinedepictedin(a).Theredarrowsrepresentthepropagation
propagation of SPPs. The incident light is coupled into SPPs through the spiral slit, and the SPPs
of SPPs. The incident light is coupled into SPPs through the spiral slit, and the SPPs generated
generated from the corresponding slits at each side have the opposite direction of propagation. The
from the corresponding slits at each side have the opposite direction of propagation. The spiral
gratingsreflectpartoftheSPPwaveduetoBraggreflection.Reproducedwithpermissionfrom[28].
CopyrightSpringer,2015.

AcombinedplasmonicstructurebyASSwithcoaxialArchimedes’spiralgratings(ASG)onboth
sidesofthegoldfilm(Figure10)hasalsobeenproposedandinvestigatedfully,whichisdesignedbased
onthesamespin-dependentpolarization-sensitiveandspin-dependentfocusingeffectoftheASS[28].
ThedesignedstructureissensitivetoincidentpolarizationofCPL,anditcanrealizethefocusingand
defocusingeffectsundertheilluminationofdifferentCPLeffectivelyowingtotheexistenceofASG.
TheadditionalASGstructuremakesmoreincidentlightcoupledintoSPPsforenhancingthefield
intensity[49]. TheincidentlightispropagatingfromtheglasssidetothemetalASSside. Byadding
theArchimedes’spiralgratingsonthebottomofthemetal,thecouplingefficiencyofincidentlightto
SPPscouldbeenhancedefficiently.Meanwhile,withthemethodofaddingASGonthetopofthemetal
film,theexocentricSPPscanbediminished,anditcandecoupleintoscatteringlight;therefore,thefocus
intensitywillbestronger.
Nanomaterials 2017, 7, 405 10 of 22
spiral gratings reflect part of the SPP wave due to Bragg reflection. Reproduced with permission
from [28]. Copyright Springer, 2015.
A combined plasmonic structure by ASS with coaxial Archimedes’ spiral gratings (ASG) on
both sides of the gold film (Figure 10) has also been proposed and investigated fully, which is
designed based on the same spin-dependent polarization-sensitive and spin-dependent focusing
effect of the ASS [28]. The designed structure is sensitive to incident polarization of CPL, and it can
realize the focusing and defocusing effects under the illumination of different CPL effectively
owing to the existence of ASG.
The additional ASG structure makes more incident light coupled into SPPs for enhancing the
field intensity [49]. The incident light is propagating from the glass side to the metal ASS side. By
adding the Archimedes’ spiral gratings on the bottom of the metal, the coupling efficiency of
Nanominacteirdiaelnst2 0li1g7h,7t ,t4o0 S5PPs could be enhanced efficiently. Meanwhile, with the method of adding ASG on1 0of21
the top of the metal film, the exocentric SPPs can be diminished, and it can decouple into scattering
light; therefore, the focus intensity will be stronger.
TheTshime suilmatuiloantiorne sruelstusltasr aeres hsohwownni nin FFiigguurree 1111.. BBotoht hthteh eeleecltercict rfiicelfdie ilndteinnstietyn sfiotry thfoer LtChPe aLnCdP and
RCPRilCluPm illiunmatiinoanticoans ecassaerse airme ipmropvroevdedo bovbivoiuouslsylyc ocommppaarreedd ttoo tthhaatt ooff tthhee ssiinngglele AASSS,S w,whihchic his ibsebtteetrt erfor
practfiocra pluratciltiitcya.l utility.

FiguFriegu11re. 1|1E. ||E2|2d disisttrriibbuuttiioonn inin thteh ze-yz--pyl-apnlea fnoer tfhoer ltehfte-hlaenftd- hspainradl psplaisrmalonpilca lsemnso. nTiocpl ceonlsu.mTno (pa,bc)o: lumn
(a,b)P:uPrue resinsignleg-lteu-rtnu rlneftl-ehfat-nhda nAdSSA; SbSo;tbtoomtt ocmolucmolnu m(cn,d)(:c ,lde)f:t-hleafnt-dh aAnSdS AsuSrSrosuunrdroedu nbdye dlebfty-hlaenfdt- hand
ArchAimrcehdimeesd’essp’i rsaplirgalr agtriantging(A (ASGSG))o onnb bootthh ssiiddeess ooff tthhee mmeteatla flilfiml;m (a;,(ca) ,Lc)CLP CilPlumilliunmatiionna; t(ibo,nd;) (RbC,dP) RCP
illumination. Reproduced with permission from [28]. Copyright Springer, 2015.
illumination.Reproducedwithpermissionfrom[28].CopyrightSpringer,2015.
3.6. Combination of ASG and MIM Waveguide
3.6. CombinationofASGandMIMWaveguide
The above reviewed structures only work at a specific wavelength and allow both RCP and
The above reviewed structures only work at a specific wavelength and allow both RCP and
LCP light transmit though the plasmonics lens. Therefore, if a structure can work in a relative
LCPblriogahdtbatrnadn asnmdi tbltohcok uCgPhL twhiethp al agsivmeno nhiacnsdleednnse.ss,T thhee rpeefrofroer,miafnaces otrf upcotluarriezactiaonn wseloercktiviintya wrilell ative
broabdeb baentdtera.n Ind 2b0l1o2c,k RC. HPoLllwinigtshwaorgtihv eetn ahl. apnrdopeodsneeds as ,htyhberipde srtfrourcmtuaren cceomofbipnoinlagr AizSaGti ownitshe alenc MtivIMity will
bebewttaevre.gIunid2e0 1[520,]R a.sH shoollwinng isnw Foirgtuhree t12a.l .Inp rtohpeior siendveasthigyabtiroindss, ttrhuec sttururectcuorme cbainn iwnogrAk SvGeryw witehlla inn MIM
wavevgisuibidlee a[5n0d] anseasrh-oinwfrnareind Friegguiorens1 2o.rI nlotnhgeeirr iwnvaevsetleignagttihosn. sB,oththe snturumcetruicrael casnimwuloartikonvse raynwd ellin
experiments have been performed to demonstrate its admirable performance of circularly
visibleandnear-infraredregionsorlongerwavelengths. Bothnumericalsimulationsandexperiments
dichroism.
haveNbaneoemnatepriealrsf 2o0r1m7, 7e, d405to demonstrateitsadmirableperformanceofcircularlydichroism. 11 of 22

Figure 12. The perspective and cross-section view of ASG with the MIM waveguide. The dimensions
Figure12.Theperspectiveandcross-sectionviewofASGwiththeMIMwaveguide.Thedimensionsof
of such a structure can be easily fabricated with state-of-the art photolithography systems.
suchastructurecanbeeasilyfabricatedwithstate-of-theartphotolithographysystems.Reproducedwith
Reproduced with permission from [50]. Copyright Optical Society of America, 2011.
permissionfrom[50].CopyrightOpticalSocietyofAmerica,2011.
The combined structure can be fabricated with the state-of-the-art photolithography systems,
and only standard thin film of three lithography levels is required for the fabrication process. The
gold film was deposited on the silicon dioxide (SiO2), and the center region of the metal spiral
gratings was cut out to form a cavity with an aperture whose cross-section was a trapezoid MIM
waveguide [51–53]. The dielectric layer of SiO2 uniformly covered the metal region, and a metal cap
was used to cover the circular aperture as shown in Figure 12. The ASG is similar to longer
wavelength antenna analogues [10], which can only transmit CPL with a specific chirality, but block
CPL with the opposite chirality. Meanwhile, the metal cap can effectively obstruct the direct
transmission of the incident light. Such a spiral configuration can concentrate the RCP light and
then radiate the energy out of the circular aperture into the far-field region. However, for the LCP
light, the field is concentrated into the plasmonic vortex, which embraces the metal cap, and finally,
the energy will be absorbed owing to the ohmic losses. These facts indicate that the novel model is a
kind of transmitting structure, and the polarization character of CPL incidence can be detected by
measuring the far-field transmission. The superiority of this designed structure makes it easy to
detect the signals by measuring the far-field transmission and to modulate the concrete operating
wavelength. By varying the incident wavelength, the transmission for RCP incidence is still larger
than that under LCP illumination in a relatively broad operating wavelength. This is why this
structure can work in a controllable operating wavelength. Meanwhile, by modulating the
parameters (spiral arm length), more incident energy can be coupled into the SPP mode, and the
total transmission can be increased correspondingly under RCP incidence.
The investigation on the influencing performances of the arm length (from 3π to 4.5π) are
shown in Figure 13. The simulation results reveal that by increasing the arm lengths, the RCP
transmission increases, while LCP transmission nearly remains constant for a relatively broad
operating wavelength, which means circular polarization selectivity can be improved with
increasing the arm lengths. The most representative parameter for evaluating the actual
performance of the designed structures is the extinction ratios. The extinction ratios can reach their
maximum when the arm length goes to 4.2π, and then, it will slightly reduce with the increased
arm length because of the slightly increasing LCP transmission. The simulated results agree well
with the measured far-field transmission, which demonstrates that such a configuration can be
utilized individually as a miniature circular polarization analyzer with a controllable bandwidth.